Constant-speed motor



C. I. HALL.

CONSTANT SPEED MOTOR.

APPLICATION FILED JAN. 28, 1920.

Patented Au 9,1921.

Inventor: Chesterl. Hall .filwlr His Attorney.

' described 1 UNITED STATES! CENTER 1. BALL, 0! FORT WAYNE,

PATENT ounce.

consrm-srnnn moron Specification of Letters Patent.

Application filed January To all whom it may concern:

Be it known that I, Cnnsrnn' I. HALL, a citizen of the United States, residin at Fort Wayne, county of Allen, State of ndiana, have invented certain new and useful Imrovements in Constant-Speed Motors, of which the following is a specification.

This invention relates to constant speed motors designed to operate at substantially uniform speed of operating characteristics within certain limits.

The object of my invention is to make the speed of the motor substantially constant irre ective 'of variations both of voltage and requency. My motor can, therefore,be advantageously used on ordinary commercial circuits where there usually are slight but comparatively frequent variations both of frequency and voltage. My motor finds aplication in certain well known types of electrical demand apparatus in which keepin device is necessary to determine the equal intervals of time during which the demand is measured, or to determine the times during which equal energy intervals are consumed. When so applied, my motor replaces the ordinary spring actuated clockwork. From this aspect, my motor is adapted to perform the same function as that in a patent granted to me uly numbered 1,234,465.

former patent mentioned above, is so arranged that even for a In my the motor comparatively large there is no percept'ble variation in speed, but a variation in frequency would produce a large variation in speed. In my present invention, I provide gives from .2 to .7 upon a variation 0 65 cycles.

In the embodiment of my invention herein illustrated and described,- I provide a magnetic structure substantially like that described in my former patent. The oppositely positioned pole pieces may also be arranged in general like those shown in that patent. The energizing coils carried by the magnetic member areso located as to distribute the lines of force properly for the purpose of assisting in the elimination of speed variation when the frequency varies between comparatively narrow limits. The shading coil torque is made adjustable by making the er cent. error in speed frequency from to temperature compensation, a

irrespective of the variation 7 a time-.

variation in voltage,

a construction which Patented Aug. 9, 1921.

2a, 1920. Serial in. 354,532.

poles relatively rotatable with respect to the magnetized member. T 0 provide automatic bimetallic therbe operatively asso of the two poles in a manthat shown in my previous mostatic element may ciated with one nor similar to patent.

For a more complete understandin invention, I provide the following description taken in connection with the accompanying drawing, in which:

Figure 1 is a diagrammatic view in perspective of an electric motor embodying my invention operatively connected to a circuit closer for closing an electric circuit at equal time intervals, and Fig. 2 is a perspective view of one of the pole pieces and its shad- .in coil.

The motor comprises a U-shaped magnetic member 5, upon each leg of which is mounted an electric current carrying coil 6., The coils 6 are shown as connected in series with each other, and are supplied with current from the conductors 7 of an alternating current circuit. The coils 6 are, furthermore, adjustable, so that the disposition and amount of the leakage flux from limb to limb of the magnetic member 5 may be properly controlled. The magnetic member carries at its ends two pole pieces 8 and 9 separated from each other by a small uniform air gap. Each pole iece carries a shading coil such as a short-circuited copper conductor 10. Each pole piece may also be independently adjusted, as, for example, by rotation about a pin 11 secured to the pole piece and inserted in a suitable aperture in the U-shaped magnetic member 5. The lower pole piece 8 may be adjusted and secured in its adjusted position independently of the other pole piece 9, which is adapted to be rotated in response tostemperature changes, so that such changes may not affect the speed of the motor. The means for accomplishing the rotation of the pole piece 9 in response to temperature changes comprises a duplex or bimetallic thermostatic member 12 secured to the pole piece, and loosely positioned at its free end in a groove 18 of a stud 19 secured to member 5. The operation and construction of this bimetallic member are identical with that disclosed in my former patant, and it is deemed unnecessary here further to describe this feature, except to state that, upon an increase of the surrounding atof my mospheric temperature, the pole piece 9 is rotated so as to increase the effective torque due to this pole piece.

A metallic disk armature 13 of conducting material, such as copper or aluminum, is sea pivotally mounted shaft 14, and air gap between haped magnetic member. The disk is furthermore subjected to the leakage flux between the two legs of the magnetic member. The short-circuited conductors are so positioned and adjusted that the proper amount of torque is exerted by the pole pieces. The rotatable shaft 14 is shown as arranged to drive a mechanism 15 for causing contacts 16 in a circuit 17 to be momentarily connected at equal intervals. The mechanism 15 here shown is the same as that described in my former patent referred to above.

In general, it may be stated that proper positioning of coils 6, so as to control the leakage flux, and of the pole results in substantially uniform speed irrespective of both voltage and frequency variation. To understand how this takes place, it is necessary to remember that the actual useful load which comprises the driving of e mechanism 15 is so slight as to be negligible. Furthermore the disk, due to the very heavy artificial load imposed by the electromagnetic drag, rotates at a very slow rate and may be considered to be practically at standstill. To secure uniform speed it is merely necessan to balance the damping load against the shading coil torque, so that e two in standstill conditions. Upon an increase of frequency, the efiective torque is varied both by the increased phase displacement due to the shading coil and by the change in total flux due to the change in impedance. This would result in a change in speed were it not for the fact" that the damping effect of the main flux is proportionately varied so as to maintain a constant relation between the forward torque and the damping, and thereis maintained constant.

Tom actual that the speed becomes constant for both values of frequency corresponding to the limits of its variation.

It is to be noted that not only is frequency variation taken care of, but variations in the impressed E. M. I compensated for. exactly the same referred to above.

I have made the explanation ree from abstruse theoretical calculations, because such calculations would have to be based'on more or less justifiable assumptions. Suflice it to say that I vide means whereby the damping load of my-device and pleces 8 and 9,

con'unction ma roduce almost I and desire to secure United States, is,--

a source a rotatable member, means for g a torque in one direction therein that is a function of the frequency of the current supplied thereto and adjustable means for creating a torque in the opposite direction that is a dissimilar t.e frequency, said latter means being so adjusted that the torque created thereby has substantially constant relation to the first mentioned torque for a relatively large frequency variation.

2. In a constant speed motor adapted to be connected to a source of variable frequency, a rotatable disk armature,

I andadapted to create a torque therein one direction, and an energizing coil for said magnetic member, said coil being ad ustable so as to cause such in a distrib of the magnetic lines of force across the armature that an electromagnetic drag is produced therein substantially equal to the torque produced by the pole pieces for a comparatively large frequency variation.

In a constant speed motor, a rotatable disk armature, a U-shaped magnetic memer aving its legs disposed over the faces of said armature, a pair of pole ieces carried by said member, a shading coll for each po e piece, so arranged as to create a torque within the armature,

as to cause such a distributmn of the ma netic lines crossing th electromagnetic drag th tially equal to the torque produced by the po e pieces for a comparatively large frevariation.

quenqy e. n a constant speed motor, a rotatable disk armature, a shaped magnetic memer having its legs disposed over the faces of said armature, a pair of adjustable pole pieces carried by said member, a shadin for each pole piece, means for adjusting one of said pole pieces in response to temperature var'ation, an.

energizin coil card by each of the l g an energizing coil for egs of the magnetic,

member, said coil being adjustable so as to cause such a distributmn of the magnetic lines crossing the armature that the electromagnetic drag therein is substantially equal to .the torque produced by the pole pieces for a comparatively large frequency variation.

5. The method of producing substantially constant speed in an electric motor irrespective of frequency variations which consists in creating a torque in one direction that is a certain function of the. frequency of the source of supply, and producing an opposing torque that is a dissimilar function of the frequency of an amount bearing a substantially constant relation to the first mentioned torque, for a relatively large variation in frequency.

In witness whereof, I' have hereunto set my hand this 21 day of January, 1920.

CHESTER I. HALL. 

